Zenith SS2712VK9 Horizontal "Breathing"

How about posting the chassis series, or module number, year of manufacture?

I tend to define ?breathing? as a uniform, repetitional slow time constant of change, while what you describe is random in its occurrences.

Well with the SS we know it?s a sheltered model and with the 27 it has a 27 inch pic tube,

and with a 12 suffix its at the very bottom of the design/features line or a table model. But we still don?t know the manufacture age ?listed on the back model tag?. or the sets module complement. But anyhow, going on in the blind. Have you observed a still/stable/fixated enough pattern to ascertain if that hoz compression is squeezing in equally from both sides. Or is there is a coke bottle type of side compression, with the most compression being in the center and bowing in less at top and bottom. If its the first symptom, the overall hoz drive/sweep level is changing. If the latter you are experiencing a cutting in and out of the pincushion correction circuitry.

I suspicion that you are starting to experience an intermittency of connection in a solder joint on a hoz or pin ckt component that inherently runs quite warm or carries a high pulsed current level thru its path, or is in the close proximity of another warm running component. What I might suggest is getting an ~ ¼-3/8 in dia solid plastic rod that is ~ 1 ft long ( Venetian blind adjustment rod, etc?[let your wife figure that one out?-12 in shorter rod]) . This will provide a protective/insulated rod to tap upon suspected components with. The set is operational with the back off and a stable still picture from a cable bulletin board type of channel or the stable self produced logo from a DVD player is utilized. Observing the reflection on a frontally placed mirror , components in the hoz sweep and pincushion circuit are light/moderately tapped while the pattern is observed for compression to pinpoint a touchy component/ connection.

Positioning is referenced while viewing from the back of the set. In most all Zeniths, the hoz sweep area and its components are at the right rear area, working forward. The chassis/module with the most troublesome pin circuitry is to the right front corner where there is a troublesome pair, of a hot running pincushion diode and a vertically mounted pincushion coil.

Lastly, and you do know *not* to French Kiss the very well insulated red high voltage wire going up to the picture tubes top insulated ultor connection from the high voltage transformer don?t you , otherwise you will be safe by your using the isolation and distancing provided with the acrylic rod.

If detected, a touchy part will justify an almost microscopic inspection of its solder connections for it being almost floating within its solder connection blob?thus necessitating a rosin fluxing and a reflow soldering with fresh solder.

Standing by

73?s de Edd

--
Edd Whatley

For those who asked for more information, the "service number" is SS2712VK9, serial number 091-25500260, manufactured in December

1990, and shows a "module replacement number" 9-896. There is no information identifiable as a "chassis number" that I can see anywhere.

Had to choose one word for short title description, and hopefully described it better in the body. Could have said "jitter", but not sure if that fits either.

Actually, it's a rather nice floor model with stereo I/O and glass doors and shelves in the bottom for VCR or component audio. I thought the "service number" SS2712VK9 would be sufficient, but if it helps serial number is 091-25500260, manufactured December 1990, "module replacement number" 9-896. Is the module replacement number what passes for a chassis number in Zenith circles?

It is changing about the same on both sides, and the amount of pin correction does not appear to be changing. As near as I can tell without a schematic, it appears to use the single big diode modulator pincushion setup. But it also has a big NP elctrolytic that most makers do not use. Maybe I start there since I can read the value and happen to have one handy. Some of the other parts like the big safety cap, for example, just have house numbers so I am not totally sure what to use for sub. I hate when they do that.

Horizontal drive looks plenty big and doesn't seem to change when it is acting up, and the HOT doesn't get excessively warm, so I think it is being switched hard enough and the problem is somewhere downstream.

I have a small paint brush with plastic handle that I use for both cleaning and tapping, and nothing seems sensitive. I've inspected the soldering pretty close and sucked off and resoldered anything that looked questionable plus a few that didn't. Replaced on principle a cap that had leaked a bit even though it checked good. So far nothing has affected the problem.

Roger the big diode and coil. I'll give them the third degree...

And about the big safety cap that only has a Zenith number on it - I'm reading about 4700 pF and ESR looks reasonable. I'm guessing it might be a 1600V polypropylene if I have to make a stab at a real world part. Does that sound right?

The big red wire has mostly not been a problem for me, but I am good at finding pinholes in the smaller white focus wire (bszzzht!) ;-)

Thanks.

When you say jitter, do you mean the edges look like a sawtooth? If yes, then replace the 22uf capacitor right next to the jungle ic on the 9v line.

If the chassis has the metal can shields in the power supply, there are three or so bad capacitors in there.

A good ESR meter will f> > > I tend to define "breathing" as a uniform, repetitional slow time

No, jitter was the word I *didn't* choose for the title, and what you describe I believe is called "piecrust", and no it isn't doing that, it just changes a little in width and not in a periodic way.

No shields and I've checked the caps. The supplies look stable and do not have excessive ripple. It does "sing" a little bit, but from the way the factory slobbered glue over all the ferrites and diodes, I'd guess that was normal for this supply.